In draft inducer blowers such as utilized in connection with furnaces and the like, it is common to provide a draft inducer including a housing and a blower wheel that is driven by an electric motor mounted on the housing and having a shaft providing a driving connection with the blower wheel within the draft inducer housing.
Most medium efficiency home furnaces (78% to 84% rated efficiency) use such draft inducer blowers to draw the combustion air through the heat exchanger and force it up the chimney. These blowers are typically handling air temperatures in the range of 400 to 450 degrees Fahrenheit. The blower housings and wheels are typically metal to handle these temperatures.
When the blower motor is mounted directly to the blower housing, the motor bearing closest to the blower housing (hereafter called the shaft-end bearing) is exposed to an excessive amount of heat both radiated from the surface of the blower housing and conducted through the motor mounting means and through the shaft of the motor. To prevent lubrication failure and extend motor life, bearing temperatures must be carefully controlled.
In an effort to minimize the heat radiated and conducted from the blower, it is common to space the electric motor away from the blower housing and add a fan blade to the motor shaft between the motor and blower. The fan blade introduces air movement through the motor and across the surface of the housing, while at the same time acting as a heat sink to remove heat conducted through the motor shaft to the shaft-end bearing. A guard is then required to prevent persons from touching the otherwise exposed fan blade.
Such a system is only marginal in controlling shaft-end bearing temperatures and unacceptable motor life is sometimes experienced. Cool air is drawn through the motor and hot air is thrown radially from the fan blade, but the hot air recirculates around the shaft end of the motor and reduces the effectiveness of the system.
Among the objectives of the present invention are to provide a draft inducer blower motor mounting including a heat shield/motor mount wherein air is directed both through and over the outside of the electric motor to cool the entire motor and especially the shaft-end bearing; wherein the heat shield/motor mount functions as a heat shield, isolating the motor from heat radiated from the surface of the blower housing; wherein the heat shield/motor mount functions to hold the electric motor to the blower housing without the need for additional construction; wherein the heat shield/motor mount covers the fan blade which is interposed between the electric motor and the draft inducer housing and protects against injury; and wherein the fan blade also acts as a heat sink to reduce heat transmitted through the motor shaft from the blower housing and functions to induce air flow to assist in cooling the electric motor.
In accordance with the invention, a draft inducer blower motor mounting and cooling construction comprising an electric motor including a housing having openings therein and a rotor mounted on a shaft, a fan blade fixed on the shaft and interposed between the motor and the draft inducer blower, and a heat shield interposed between the motor housing and the fan blade. The heat shield is fastened to the electric motor and to the housing of the inducer blower and has portions spaced from the blower housing. The heat shield preferably includes a portion surrounding at least a part of the motor housing such that rotation of the fan blade draws cooling air through the electrical motor and about the housing of the electric motor and thereafter radially outwardly between the heat shield and the inducer blower housing to cool the electric motor and the shaft end bearing nearest the inducer housing. In another form, the portion surrounding the motor housing is eliminated.